1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to a nitride semiconductor light-emitting device.
2. Discussion of the Related Art
A nitride semiconductor light-emitting device includes ultraviolet, blue, and green light-emitting regions. Especially, a GaN-based nitride semiconductor light-emitting device can be applied to an optical device of red/green light-emitting diode (LED), and an electronic device corresponding a high-speed switching or high-power device of MESFET (Metal Semiconductor Field Effect Transistor) or HEMT (Hetero Junction Field-Effect Transistor).
FIG. 1 is a cross section view illustrating a nitride semiconductor light-emitting device according to the related art.
As shown in FIG. 1, the nitride semiconductor light-emitting device 100 according to the related art includes a substrate 110, a buffer layer 120, an undoped semiconductor layer 130, an N-type nitride semiconductor layer 140, an active layer 150, a P-type nitride semiconductor layer 160, a transparent electrode layer 170, a P-type electrode 180 on the transparent electrode layer 170, and an N-type electrode 190 on the N-type nitride semiconductor layer 140 exposed by etching predetermined portions of the active layer 150 and the P-type nitride semiconductor layer 160.
In case of the nitride semiconductor light-emitting device 100 according to the related art shown in FIG. 1, since the P-type electrode 180 and the N-type electrode 190 are formed on the same plane, it is difficult to realize a uniform current distribution. Thus, as shown in FIG. 2, a current crowding phenomenon occurs in a region near to the N-type electrode 190. This current crowding phenomenon may cause various problems, for example, deterioration of the nitride semiconductor light-emitting device, the increase of forward voltage, and electrostatic discharge (ESD).
In order to overcome the aforementioned problems caused by the current crowding phenomenon, there has been proposed a method for increasing the number of electrode fingers. The increased number of electrode fingers enables the uniform current distribution. However, a light-emitting area is decreased due to the increased number of electrode fingers.
In addition, the nitride semiconductor light-emitting device according to the related art has problems such as total reflection of light, and reduction of light extraction efficiency caused by light absorption in the active layer and the electrode.